1. One too many beers and an exposed curb.
2. Ice in parking lots. (Like banana peels in cartoons)
3. Having my teacher make me do one for dramatic effect.
4. Pushing on a door that someone pulls open a split second before I touch it.
5. One kiai as tori. (I think I forgot to brush my teeth)

Makes you kind of re-evaluate the term "touch", doesn't it? And who is doing the throwing?